Abstract

Orogenic curvature is a common feature in many mountain belts and is strongly linked to the magnitude, direction, and mechanics of crustal shortening. Determining how formation of the Bolivian orocline influenced crustal deformation in the central Andes has direct implications for geodynamics of the high-elevation Altiplano plateau. This study presents new reconstructions of the Bolivian orocline constrained by shortening estimates, thermochronology, regional paleomagnetic data, and strain data from lat 12°S to 22°S. The reconstructions investigate paleomagnetically permissible orocline limb rotations of 0°, 6°, and 13° on the kinematic compatibility of shortening constraints. Deformation was restored in 5 m.y. steps from 50 to 0 Ma, and kinematic compatibility was quantified based on the area of map-view overlap at each step. No limb rotation resulted in 14,000 km2 of overlap, while 13° limb rotations and 50 km of orogen-parallel displacement on known strike-slip faults reduce overlap to 3000 km2. The preferred model builds on these results by imposing additional rotations at the orocline core and displacement on the Cochabamba fault. This model reduces overlap to 1600 km2 but predicts map-view shortening estimates 70–90 km greater in the northern limb and 20–30 km greater in the southern limb than determined from cross sections. Of the modeled increase, ∼20 km is due to limb rotation, while the remaining 50–70 km is due to transpressional shortening on the Cochabamba and Rio Novillero faults. Total shortening in the preferred model is 370 km in the northern limb, 380 km at the orocline core, and 300–350 in the southern limb.